CN112930490A

CN112930490A - Structured lighting device

Info

Publication number: CN112930490A
Application number: CN201980069929.0A
Authority: CN
Inventors: 詹姆斯.艾勒森
Original assignee: Ams Sensors Asia Pte Ltd
Current assignee: Ams Osram AG; Ams Sensors Asia Pte Ltd
Priority date: 2018-10-22
Filing date: 2019-10-21
Publication date: 2021-06-08
Also published as: US20210391693A1; DE112019005258T5; WO2020085999A8; WO2020085999A1

Abstract

An illumination device, comprising: an emissive layer comprising a semiconductor-based light emitter; and an optical layer disposed on the emissive layer. The optical layer includes an optical element, such as a lens, that is at least partially aligned with the semiconductor-based light emitter. The optical layer is formed of a material having a negative Coefficient of Thermal Expansion (CTE). For example, a semiconductor-based light emitter is configured to emit light at a wavelength λ, where the pitch p of the MLA, the thickness z of the optical layer, and the wavelength λ satisfy a predefined relationship.

Description

Structured lighting device

Background

Structured light is light having a specific pattern. Illumination devices that generate structured light may be used for three-dimensional (3-D) imaging, which has applications in different fields such as automotive vehicles and face recognition.

Disclosure of Invention

In one aspect, a lighting device includes an emissive layer comprising a semiconductor-based light emitter; and an optical layer disposed on the emissive layer. The optical layer includes optical elements at least partially aligned with the semiconductor-based light emitters. The optical layer is formed of a material having a negative Coefficient of Thermal Expansion (CTE).

Implementations may include one or more of the following features.

The optical element and the optical layer may be monolithic. For example, they are in the form of monolithic layers.

The optical element comprises a lens.

The optical layer includes a micro-lens array (MLA) including a plurality of lenses.

The MLA and the optical layer may be monolithic. For example, they are in the form of monolithic layers.

The emission layer includes a plurality of semiconductor-based light emitters, each of the one or more lenses of the MLA being at least partially aligned with a respective semiconductor-based light emitter.

The semiconductor-based light emitter is configured to emit light at a wavelength λ, and wherein the pitch p of the MLA, the thickness z of the optical layer, and the wavelength λ satisfy a predefined relationship.

The pitch p, thickness z and wavelength λ satisfy a predefined relationship z ═ p ^2/λ.

In response to a change in temperature, the semiconductor-based light emitter is configured to emit light at a second wavelength λ 2, and the optical layer is configured to have a thickness z2, and wherein the pitch p, the second thickness z2, and the wavelength λ 2 satisfy a predefined relationship.

Semiconductor-based optical transmitters include semiconductor lasers, such as vertical-cavity surface-emitting lasers (VCSELs).

In some cases, the unitary structure of the MLA and the optical layer can prevent the MLA from detaching from the optical layer. This may prevent direct exposure of a person to the laser, for example.

The optical layer includes glass, polymer, or a composite material having a negative CTE.

The optical layer includes a wafer bonded (bond) to the emissive layer, the wafer being formed of a material having a negative CTE, and the wafer including optical elements.

The optical layer includes a film disposed on the emissive layer, the film being formed of a material having a negative CTE, and the optical element is formed in the film.

The material of the optical layer has a thickness of-1X 10^-7and-1X 10^-5℃^-1With a CTE therebetween.

The material of the optical layer has a negative CTE in a direction perpendicular to the plane of the optical layer.

The illumination device forms part of a three-dimensional (3-D) imaging system, such as a 3-D imaging system for a vehicle or for a mobile computing device.

In one aspect, a method of manufacturing a lighting device includes disposing an optical layer on an emissive layer comprising a semiconductor-based light emitter, including at least partially aligning an optical element of the optical layer with the semiconductor-based light emitter, the optical layer formed of a material having a negative CTE.

Implementations may include one or more of the following features.

Disposing the optical layer on the emissive layer includes bonding a wafer to the emissive layer, the wafer being formed of a material having a negative CTE, and the wafer including an optical element.

Bonding the wafer to the emitter layer includes bonding a glass wafer having a negative CTE to the emitter layer.

Disposing an optical layer on the emissive layer comprises depositing a layer of a material having a negative CTE onto the emissive layer; and forming an optical element in the deposited layer.

The optical element is integrally integrated with the optical layer (incorporate). For example, the optical element and the optical layer are formed as an integral layer.

The optical element is formed using a microfabrication technique such as photolithography, for example, by which the optical element is formed on one side of the optical layer.

Depositing a layer of a material having a negative CTE onto the emissive layer includes depositing a polymer having a negative CTE onto the emissive layer.

The method includes forming an emissive layer.

The emitting layer comprises a VCSEL.

The optical element comprises a lens.

The optical layer includes an MLA comprising a plurality of lenses, and wherein disposing the optical layer on the emissive layer includes at least partially aligning each of the one or more lenses of the MLA with a respective semiconductor-based light emitter.

The semiconductor-based optical transmitter is configured to transmit light at a wavelength λ. Disposing the optical layer on the emissive layer includes disposing the optical layer at a thickness z that satisfies a predefined relationship between the thickness z, the pitch p of the MLA, and the wavelength λ.

Disposing the optical layer on the emissive layer includes disposing the optical layer at a thickness z that satisfies a predefined relationship z ═ p ^2/λ.

In one aspect, a 3-D imaging system includes an illumination device configured to illuminate an object with a pattern of light, the illumination device including an emission layer comprising a semiconductor-based light emitter; and an optical layer disposed on the emissive layer. The optical layer includes optical elements at least partially aligned with the semiconductor-based light emitters. The optical layer is formed of a material having a negative CTE;

a sensor configured to capture an image of the illuminated object. The 3-D imaging system also includes one or more computing devices configured to determine a 3-D shape of the object based on the captured images.

Implementations may include one or more of the following features.

The sensor comprises a camera.

The one or more computing devices are configured to determine a 3-D mapping of the region based on the captured image.

The one or more computing devices are configured to perform a facial recognition process based on the determined 3-D shape of the object.

The structured lighting devices described herein may have one or more of the following advantages. An optical layer formed of a material having a negative thermal expansion coefficient may contract with an increase in temperature, counteract a wavelength shift caused by the increase in temperature, and enable a high-quality structured light output to be maintained.

Drawings

Fig. 1 is a diagram of a structured light illumination apparatus.

Fig. 2A and 2B are diagrams of a structured light illumination device.

Fig. 3 is a flowchart.

Fig. 4 is a diagram of a vehicle.

Fig. 5A and 5B are diagrams of a mobile computing device.

Detailed Description

An illumination device capable of producing structured light is described herein, for example, for three-dimensional (3-D) imaging applications such as mapping or facial recognition. The illumination devices described herein include a light emitter and one or more optical elements (e.g., a microlens array), at least one of which is at least partially aligned with the light emitter. The light emitter is separated from the optical element by an optical layer formed of a material having a negative Coefficient of Thermal Expansion (CTE).

Referring to fig. 1, structured light illumination apparatus 100 emits a pattern of light, sometimes referred to as structured light. Structured light can be used for 3-D imaging. For example, the structured light illumination device 100 may form part of a 3-D imaging system of a vehicle, such as a partially autonomous or fully autonomous vehicle. The structured light illumination device 100 may form part of a 3-D imaging system of a mobile computing device, such as a mobile phone, for example for facial recognition or environmental mapping.

The structured light illumination device 100 comprises an emission layer 102, the emission layer 102 comprising a semiconductor-based optical emitter 104, such as a semiconductor laser, e.g. a Vertical Cavity Surface Emitting Laser (VCSEL) or a side emitting semiconductor laser; or a diode such as a laser diode or a Light Emitting Diode (LED). For example, the emissive layer 102 may be a wafer, such as a silicon wafer, in which the light emitters 104 are fabricated. The light emitter 104 emits light 105 from an emission surface 106 of the emission layer 102. The light may be visible light, infrared light or ultraviolet light. In some examples, the emission layer 102 may include a plurality of light emitters 104, such as a one-dimensional or two-dimensional array of light emitters 104.

An optical layer 108 is disposed on the emissive layer 102. Optical layer 108 may be transparent to the wavelength of light emitted from light emitter 104. In some examples, the optical layer may be a wafer attached to the emissive layer 102 by a wafer attachment technique (e.g., wafer bonding). In some examples, the optical layer may be a thin film deposited on the emissive layer 102 by a thin film deposition technique.

The optical layer 108 includes one or more optical elements 110, such as lenses. For example, as shown in fig. 1, the optical layer 108 may include an array 112 of a plurality of optical elements 110 (e.g., a plurality of lenses), sometimes referred to as a microlens array (MLA). The structured light emission from the lighting device 100 originates from an interference pattern generated by interference of light propagating from different ones of the optical elements 110 in the MLA 112 such that the contrast of the structured light remains substantially constant over the far field of the MLA 112, e.g., at least as far as 5 centimeters, 10 centimeters, 50 centimeters, 100 centimeters or more.

The one or more optical elements 110 and the optical layer 108 may be monolithic, with the one or more optical elements 110 being formed on one side of the optical layer 108 by, for example, a micro-machining process. An example of such a microfabrication process is photolithography. In the case where the light emitter 104 is a laser, this integral arrangement has the benefit of improved eye safety. For example, in some cases, the unitary structure of the one or more optical elements 110 and the optical layer 108 prevents the one or more optical elements 110 from being detached from the optical layer 108, for example, thereby preventing a person from being directly exposed to the light 105. In other words, the overall arrangement discussed herein provides improved eye safety because the MLA 112 is less likely to move away from the VCSEL assembly, thereby preventing direct user exposure to the laser beam. It will be appreciated that this integral or integrated arrangement described with reference to figure 1 may be applied to subsequent figures.

The MLA 112 may be a one-dimensional array of lenses 110 or a two-dimensional array of lenses 110. The lenses 110 of the MLA 112 may be transmissive microlenses or reflective microlenses. The transmissive microlens is transparent to at least a portion of the light emitted from the light emitter 104 such that the light propagates through the microlens. The transmissive microlenses may be diffractive microlenses or refractive microlenses. For example, the transmissive microlenses may be athermalized (athermalized) microlenses or other hybrid lenses. The reflective microlenses reflect at least a portion of the light emitted from the light emitters 104. The reflective microlenses may have smooth curved surfaces, or may be constructed with diffractive structures. The microlenses may be convex or concave.

At least one of the optical elements 110 is at least partially aligned with the light emitter 104. An optical element at least partially aligned with light emitter 104 is positioned to receive at least some of the light emitted by light emitter 104. In the example of fig. 1, three

optical elements

10a, 10b, 10c are at least partially aligned with the light emitter 104.

The thickness z of the optical layer 108, the pitch p of the MLAs 112, and the wavelength λ of light emitted from the light emitters 104 affect the characteristics of light emitted from the illumination device 100. For example, when the thickness z, the pitch p, and the wavelength λ satisfy the target relationship, a high-contrast spot is generated in the emitted light, which means that the structured light is emitted from the illumination device 100. When the thickness z, the pitch p, and the wavelength λ do not satisfy the relationship, the structural quality of the emitted light may be reduced, for example, the size of the light spot may be increased or the contrast may be reduced, and the emitted light may not be suitable for structured light applications.

The target relationship between thickness z, pitch p and wavelength λ can be characterized by equation (1), referred to as Lau equation:

when the thickness z, pitch p and wavelength λ satisfy formula (1), a high contrast light spot is generated and usable structured light is emitted from the illumination device. When the formula (1) is not satisfied, the quality of emitted light may be degraded.

By satisfying equation (1), we mean that the values of z, p, and λ are such that equation (1) is satisfied within threshold value X, i.e.

For example, equation (1) may be considered satisfied for X values between 0.95 and 1.05, e.g., between 0.98 and 1.02 or between 0.99 and 1.01. The value of the threshold X may depend on various factors, such as an acceptable amount of contrast loss or suitability for the intended application of the lighting device 100Spot size of the emitted light.

In some examples, the wavelength λ referred to in equation (1) is a single wavelength generated by the optical transmitter 104, such as when the optical transmitter 104 generates light at a single wavelength (e.g., when the optical transmitter 104 is a laser). In some examples, the wavelength λ of equation (1) may be any emission wavelength, such as a peak wavelength in an emission wavelength spectrum, for example, when the optical transmitter 104 produces multiple wavelengths.

The pitch p of the MLA 112 may be between about 5 microns and about 250 microns, such as between about 10 microns and about 150 microns.

Further description of generating structured light from light emitters and MLAs can be found in WO 2016/122404, the contents of which are incorporated herein by reference in their entirety.

During operation of the structured light illumination apparatus 100, the temperature of the light emitter 104 may increase. For example, if the optical layer 108 is a poor thermal conductor, the heat generated by the light emission is not easily dissipated, resulting in an increase in the temperature of the light emitter 104. The increase in temperature of optical transmitter 104 causes the wavelength emitted from optical transmitter 104 to increase. In a specific example, the wavelength emitted from the VCSEL can be increased by approximately 0.07 nanometers/deg.c. In another specific example, the wavelength emitted from the edge-emitting device may be increased by approximately 0.35 nanometers/deg.C.

In order for the illumination device 100 to continue to satisfy equation (1) even as the wavelength λ increases, the optical layer 108 may be formed of a material having a negative Coefficient of Thermal Expansion (CTE). A negative CTE material is a material that contracts with increasing temperature. This means that a temperature increase that results in an increase in wavelength λ will also result in a decrease in the thickness z of the optical layer 108, dynamically repositioning the optical element 110 relative to the light emitter 102 such that equation (1) remains satisfied.

Referring to FIG. 2A, in a specific example, a structured light illumination apparatus 100 includes a temperature T at an initial temperature₁At initial wavelength λ of 850 nm₁An operating VCSEL 104. The VCSEL 104 is characterized by a wavelength shift of 0.07 nanometers/deg.c. The optical layer 108 has an initial thickness z of 2.94 millimeters₁And the MLA 112 has a pitch p of 50 microns. The optical layer 108 is composed ofCTE of-1X 10^-5Is formed of the material of (1).

Referring also to fig. 2B, during operation, the VCSEL and optical layer 108 experience a temperature increase of 71 ℃ during operation, reaching a temperature T₂Resulting in a wavelength shift of +5 nm to a shifted wavelength λ of 855 nm₂. The increase in temperature causes the thickness of the optical layer 108 to shrink by 2.09 microns to a shrunk thickness z₂2.9379 nm (original thickness z)₁A small difference value az). Shrinkage thickness z₂And offset wavelength lambda₂Satisfying equation (1), this means that the structured nature of the illumination emitted from the illumination device 100 is maintained despite the increase in emission wavelength caused by heat.

In contrast, if the optical layer 108 in the above example is formed of a material having a positive coefficient of thermal expansion, the thickness of the optical layer will increase with increasing temperature. For example, an optical layer 108 formed of sapphire (a positive CTE material) will increase in thickness up to 1 micron in response to a temperature increase of 71 ℃. The combination of the +5 nm wavelength shift and the increase in optical layer thickness 108 will result in the heated illumination device 100 failing to satisfy equation (1), meaning that the spot size or spot contrast produced from the illumination device is insufficient for structured light applications.

Optical layer 108 may be formed of any negative CTE material that is substantially transparent to the wavelengths emitted by light emitter 102. For example, the optical layer 108 may be made of a negative CTE glass material (e.g., a glass-ceramic material), a negative CTE polymer, or a composite material having a negative CTE (e.g., a composite of a polymer and an inorganic material). In some examples, the optical layer 108 may have a thickness of about-1 x 10^-7And about-1X 10^-5With a CTE therebetween.

Example materials with negative CTE include: comprising Li₂O—Al₂O₃—SiO₂Glass-ceramic of (1), comprising ZnO-Al₂O₃—SiO₂Glass-ceramic of (1), comprising Li₂Glass-ceramics of O and BaO, including Al₂O₃And BaO or a glass-ceramic comprising Li₂O—Al₂O₃—SiO₂BaO glass-ceramics. For example, an exemplary negative CTE material is in the United statesAs described in patent No. 6,521,556, the contents of which are incorporated herein by reference in their entirety.

In some examples, the optical layer 108 may have an isotropic CTE. In some embodiments, the optical layer 108 may have an anisotropic CTE, wherein the CTE in a direction perpendicular to the emitting surface 106 of the emitting layer 102 is negative, and the CTE in a direction parallel to the emitting surface 106 of the emitting layer 102 may be positive or negative. For example, an optical layer formed from a single crystal material may have an anisotropic CTE.

Referring to fig. 3, to fabricate a structured light illumination device, one or more optical emitters, such as VCSELs, side-emitting semiconductor lasers, laser diodes, or other types of optical emitters (300), are formed in an emission layer of a substrate, such as a silicon wafer. An optical layer formed of a material having a negative CTE is disposed on the emissive layer (302). The optical elements of the optical layer are at least partially aligned (304) with the light emitters. In some examples, the optical layer is a wafer in which the optical elements have been pre-formed, and the wafer is bonded to the emissive layer by a wafer bonding technique. In some examples, the optical layer is deposited as a thin film on the emissive layer, and the optical elements are formed in the optical layer, for example, using integrated circuit processing techniques such as photolithography and etching.

Referring to fig. 4, in some examples, a structured light illumination device 400, such as illumination device 100 of fig. 1, may be mounted on a vehicle 402, such as a partially autonomous or fully autonomous vehicle. The vehicle may be a land-based vehicle (as shown), such as an automobile or truck; an aircraft, such as a drone; or water-based vehicles such as boats or submarines. In the case of a partially or fully autonomous vehicle 402, the structured light illumination apparatus 400 may form part of a 3-D imaging system 404, the 3-D imaging system 404 including an imaging component such as a sensor 406 (e.g., a camera). The 3-D imaging system 404 including the structured light illumination apparatus 400 may be used for 3-D mapping of an environment, such as a vehicle 402. For example, the structured light illumination device 400 may be used to illuminate an object 408, such as an object in or near a road on which the vehicle 402 is traveling, and the sensor 406 may be used to capture an image of the illuminated object 408. The captured images may be provided to a computing device 410, for example, including one or more processors, the computing device 410 determining a 3-D shape of the object based on the captured images. By determining the 3-D shape of various objects, a map of the vehicle environment may be determined and used to control partial or full autonomous operation of the vehicle 402.

Referring to fig. 5A, in some examples, a structured light illumination device 500, such as illumination device 100 of fig. 1, may be mounted on or incorporated into a front side of a mobile computing device 502, such as a cell phone, tablet, or wearable computing device. The front side of the mobile device 502 is the side of the device that includes the screen 506. The structured light illumination apparatus 500 can be integrated into a front side imaging system 508, the front side imaging system 508 including an imaging component such as a sensor 510 (e.g., a camera). The frontal imaging system 508 including the structured light illumination apparatus 500 may be used for 3-D imaging applications, such as for facial recognition. For example, the structured light illumination apparatus 500 may be used to illuminate a person's face 512, and the sensor 510 may be used to capture an image of the face 512. The captured images may be provided to one or more processors 514, with one or more processors 514 being, for example, in mobile device 502 or remote (e.g., a cloud-based processor). The one or more processors 514 may perform facial recognition processing on the image of the face 512.

Referring to fig. 5B, in some examples, a structured light illumination device 550, such as illumination device 100 of fig. 1, may be mounted on a back side of mobile computing device 552. The back side is the side of the device opposite the front side, e.g. the side not comprising the screen. The structured light illumination device 550 can be integrated into a backside imaging system 558, the backside imaging system 508 including an imaging component such as a sensor 560 (e.g., a camera). The backside imaging system 558 including the structured light illumination device 550 may, for example, be used for 3-D imaging applications, for example for object recognition or for environmental mapping, for example mapping of a room. For example, the structured light illumination device 550 may be used to illuminate an object 562 in a room or other environment, and the sensor 560 may be used to capture an image of the object 562. The captured images may be provided to one or more processors 564, for example, in the mobile device 552 or remotely (e.g., a cloud-based processor). The one or more processors 564 may determine a 3-D shape of the object based on the captured images. The determined 3-D shape may be used by the one or more processors 564 to perform an object recognition process or may be used in combination with the determined 3-D shape of one or more other objects to develop a 3-D mapping of the room.

Structured light illumination devices such as those described herein may be incorporated into other devices, including game consoles, distance measuring devices, surveillance devices, and other devices.

A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, some of the steps described above may be order independent and may therefore be performed in an order different than that described.

Other implementations are within the scope of the following claims.

Claims

1. An illumination device, comprising:

an emission layer including a semiconductor-based light emitter; and

an optical layer disposed on the emissive layer, the optical layer including optical elements at least partially aligned with the semiconductor-based light emitter, the optical layer formed of a material having a negative Coefficient of Thermal Expansion (CTE).

2. The illumination device of claim 1, wherein the optical element and the optical layer are monolithic.

3. The lighting device of claim 1 or 2, wherein the optical element comprises a lens.

4. The illumination device of claim 3, wherein the optical layer comprises a Micro Lens Array (MLA) comprising a plurality of lenses.

5. The illumination device of claim 4, wherein the emissive layer comprises a plurality of semiconductor-based light emitters, each of the one or more lenses of the MLA being at least partially aligned with a respective semiconductor-based light emitter.

6. The illumination device of claim 4 or 5, wherein the semiconductor-based light emitter is configured to emit light of a wavelength λ, and wherein the pitch p of the MLA, the thickness z of the optical layer, and the wavelength λ satisfy a predefined relationship.

7. The illumination device of claim 6, wherein the pitch p, the thickness z, and the wavelength λ satisfy a predefined relationship

8. The lighting device according to claim 6 or 7, wherein the semiconductor-based light emitter is configured to emit a second wavelength λ in response to a change in temperature₂And the optical layer is configured to have a thickness z₂And wherein said pitch p, said second thickness z₂Said wavelength λ₂The predefined relationship is satisfied.

9. The illumination device of any one of claims 5 to 8, wherein the MLA and the optical layer are monolithic.

10. A lighting device according to any one of the preceding claims, wherein the semiconductor-based light emitter comprises a semiconductor laser.

11. The illumination device of claim 10, wherein the semiconductor laser comprises a Vertical Cavity Surface Emitting Laser (VCSEL).

12. The illumination device of any one of the preceding claims, wherein the optical layer comprises glass having a negative CTE.

13. The illumination device of any one of the preceding claims, wherein the optical layer comprises a polymer having a negative CTE.

14. The illumination device of any one of the preceding claims, wherein the optical layer comprises a composite material having a negative CTE.

15. The illumination device of any one of the preceding claims, wherein the optical layer comprises a wafer bonded to an emissive layer, the wafer being formed of a material having a negative CTE, and the wafer comprising the optical element.

16. The illumination device of any one of the preceding claims, wherein the optical layer comprises a film disposed on the emissive layer, the film being formed of a material having a negative CTE, and the optical element being formed in the film.

17. The illumination device of any one of the preceding claims, wherein the material of the optical layer has a refractive index in the range of-1 x 10^-7and-1X 10^-5℃^-1With a CTE therebetween.

18. The illumination device of any one of the preceding claims, wherein the material of the optical layer has a negative CTE in a direction perpendicular to the plane of the optical layer.

19. The illumination device of any one of the preceding claims, wherein the illumination device forms part of a three-dimensional (3-D) imaging system.

20. The illumination device of claim 19, wherein the illumination device forms part of a 3-D imaging system for a vehicle.

21. The illumination device of claim 19 or 20, wherein the illumination device forms part of a 3-D imaging system for a mobile computing device.

22. A method of manufacturing a lighting device, comprising:

disposing an optical layer on an emission layer comprising a semiconductor-based light emitter, including at least partially aligning an optical element of the optical layer with the semiconductor-based light emitter, the optical layer formed of a material having a negative CTE.

23. The method of claim 22, wherein disposing the optical layer on the emissive layer comprises bonding a wafer to the emissive layer, the wafer being formed of a material having a negative CTE, and the wafer including the optical element.

24. The method of claim 23, wherein bonding a wafer to the emissive layer comprises bonding a glass wafer having a negative CTE to the emissive layer.

25. The method of any one of claims 22-24, wherein disposing the optical layer on the emissive layer comprises:

depositing a layer of a material having a negative CTE onto the emissive layer; and

forming the optical element in the deposition layer.

26. The method of any one of claims 22 to 25, further comprising integrally integrating the optical element with the optical layer.

27. The method of claim 25 or 26, wherein the optical element is integrated with the optical layer by a microfabrication technique.

28. The illumination device of claim 26 or 27, wherein the optical element is formed by photolithography.

29. The method of any one of claims 25 to 28, wherein depositing a layer of a material having a negative CTE onto the emissive layer comprises depositing a polymer having a negative CTE onto the emissive layer.

30. A method according to any one of claims 22 to 29, comprising forming the emissive layer.

31. The method of any of claims 22 to 30, wherein the emitting layer comprises a VCSEL.

32. The method of any one of claims 22 to 31, wherein the optical element comprises a lens.

33. The method of claim 32, wherein the optical layer comprises an MLA comprising a plurality of lenses, and wherein disposing the optical layer on the emissive layer comprises at least partially aligning each of one or more lenses of the MLA with a respective semiconductor-based light emitter.

34. The method defined in claim 33 wherein the semiconductor-based optical emitter is configured to emit light at a wavelength λ and wherein disposing the optical layer on the emitting layer comprises disposing the optical layer at a thickness z that satisfies a predefined relationship between the thickness z, the pitch p of the MLA, and the wavelength λ.

35. The method of claim 34, wherein disposing the optical layer on the emissive layer comprises to satisfy a predefined relationship

Is provided with the optical layer.

36. A 3-D imaging system comprising:

an illumination device configured to illuminate an object with a pattern of light, the illumination device comprising:

an emission layer including a semiconductor-based light emitter; and

an optical layer disposed on the emissive layer, the optical layer comprising optical elements at least partially aligned with the semiconductor-based light emitter, the optical layer formed of a material having a negative CTE;

a sensor configured to capture an image of an illuminated object; and

one or more computing devices configured to determine a 3-D shape of the object based on the captured images.

37. The 3-D imaging system of claim 36, wherein the sensor comprises a camera.

38. The 3-D imaging system of claim 36 or 37, wherein the one or more computing devices are configured to determine a 3-D mapping of regions based on the captured images.

39. The 3-D imaging system of any of claims 36 to 38, wherein the one or more computing devices are configured to perform facial recognition processing based on the determined 3-D shape of the object.